Computational Study on Ring Saturation of 2‑Hydroxybenzaldehyde Using Density Functional Theory

Bio-oil produced from pyrolysis of lignocellulosic biomass consists of several hundreds of oxygenated compounds resulting in a very low quality with poor characteristics of low stability, low pH, low stability, low heating value, high viscosity, and so on. Therefore, to use bio-oil as fuel for vehicles, it needs to be upgraded using a promising channel. On the other hand, raw bio-oil can also be a good source of many specialty chemicals, e.g., 5-HMF, levulinic acid, cyclohexanone, phenol, etc. In this study, 2-hydroxybenzaldehyde, a bio-oil component that represents the phenolic fraction of bio-oil, is considered as a model compound and its ring saturation is carried out to produce cyclohexane and cyclohexanone along with various other intermediate products using density functional theory. The geometry optimization, vibrational frequency, and intrinsic reaction coordinate calculations are carried out at the B3LYP/6-311+g­(d,p) level of theory. Furthermore, a single point energy calculation is performed at each structure at the M06-2X/6-311+g­(3df,2p)//B3LYP/6-311+g­(d,p) level of theory to accurately predict the energy requirements. According to bond dissociation energy calculations, the dehydrogenation of formyl group of 2-hydroxybenzaldehyde is the least energy demanding bond cleavage. The production of cyclohexane has a lower energy of activation than the production of cyclohexanone

Quantum chemical study on gas phase decomposition of ferulic acid

<p>Ferulic acid, representing phenolic fraction of bio-oil, is considered to be a model compound in this study for its decomposition into various end products such as ethylbenzene, eugenol, <i>cis</i>-isoeugenol, vanillin, 4-ethylguaiacol, guaiacol, and acetovanillone using density functional theory approach. Results of bond dissociation energies indicate that cleavage of methyl group from ferulic acid is the lowest energy-demanding bond scission amongst all 14 bond cleavages. Primary end product by decomposition of ferulic acid is found to be ethylbenzene and its production occurs through the formation of intermediate products such as 4-hydroxycinnamic acid, cinnamic acid and styrene. Demethoxylation of ferulic acid gives rise to the production of 4-hydroxycinnamic acid which further undergoes the formation of cinnamic acid by dehydroxylation reaction route. The formation of cinnamic acid in this study is carried out using three reaction schemes 1–3 and its further reduction to ethylbenzene is performed using two reaction possibilities. Finally, favourable pathway is found to be decarboxylation of cinnamic acid to produce vinylbenzene followed by the production of ethylbenzene using hydrogenation of C=C chain double bond. Furthermore, thermochemistry of each reaction scheme is performed at atmospheric pressure and at a wide range of temperature of 598–898 K.</p